Physical Processes in Earth and Environmental Sciences Phần 1 pdf

Mike Leeder Marta Pérez-ArluceaPhysical Processes in Earth and Environmental Sciences Blackwell Publishing... Physical Processes in Earth and Environmental Sciences... Mike Leeder Marta

Mike Leeder Marta Pérez-Arlucea

Physical Processes in Earth and Environmental Sciences

Blackwell

Publishing

Physical Processes in Earth and Environmental Sciences

Dedicated to our parents

Cruz ArluceaNorman LeederEvelyn PattersonAlbino Pérez

Mike Leeder Marta Pérez-Arlucea

Physical Processes in Earth and Environmental Sciences

Blackwell

Publishing

© 2006 by Blackwell Publishing

350 Main Street, Malden, MA 02148-5020, USA

9600 Garsington Road, Oxford OX4 2DQ, UK

550 Swanston Street, Carlton, Victoria 3053, Australia The right of Mike Leeder and Marta Pérez-Arlucea to be identified as the Authors of this Work has been asserted in accordance with the UK

Copyright, Designs, and Patents Act 1988.

All rights reserved No part of this publication may be reproduced, stored

in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs, and Patents Act 1988, without the

prior permission of the publisher.

First published 2006 by Blackwell Publishing Ltd

1 2006

Library of Congress Cataloging-in-Publication Data

Leeder, M R (Mike R.) Physical processes in Earth and environmental sciences/Mike Leeder,

Marta Pérez-Arlucea.

p cm.

Includes bibliographical references and index.

ISBN-13: 978-1-4051-0173-8 (pbk : acid-free paper) ISBN-10: 1-4051-0173-3 (pbk : acid-free paper)

1 Geodynamics 2 Earth sciences–Mathematics I Pérez-Arlucea,

Marta II Title.

QE501.L345 2006 550–dc22 2005018434

A catalogue record for this title is available from the British Library.

For further information on Blackwell Publishing, visit our website:

www.blackwellpublishing.com

Preface Acknowledgments

Chapter 1 Planet Earth and Earth systems, 1

1.1 Comparative planetology, 11.2 Unique Earth, 3

1.3 Earth systems snapshots, 51.4 Measuring Earth, 71.5 Whole Earth, 101.6 Subtle, interactive Earth, 14Further reading, 16

Chapter 2 Matters of state and motion, 18

2.1 Matters of state, 182.2 Thermal matters, 202.3 Quantity of matter, 242.4 Motion matters: kinematics, 262.5 Continuity: mass conservation of fluids, 33Further reading, 35

Chapter 3 Forces and dynamics, 36

3.1 Quantity of motion: momentum, 363.2 Acceleration, 38

3.3 Force, work, energy, and power, 403.4 Thermal energy and mechanical work, 453.5 Hydrostatic pressure, 49

3.6 Buoyancy force, 523.7 Inward acceleration, 553.8 Rotation, vorticity, and Coriolis force, 573.9 Viscosity, 61

3.10 Viscous force, 633.11 Turbulent force, 653.12 Overall forces of fluid motion, 673.13 Solid stress, 71

3.14 Solid strain, 833.15 Rheology, 92Further reading, 101

Contents

Chapter 4 Flow, deformation, and transport, 102

4.1 The origin of large-scale fluid flow, 1024.2 Fluid flow types, 105

4.3 Fluid boundary layers, 1094.4 Laminar flow, 111

4.5 Turbulent flow, 1134.6 Stratified flow, 1174.7 Particle settling, 1194.8 Particle transport by flows, 1214.9 Waves and liquids, 125

4.10 Transport by waves, 1314.11 Granular gravity flow, 1334.12 Turbidity flows, 1384.13 Flow through porous and granular solids, 1424.14 Fractures, 144

4.15 Faults, 1564.16 Solid bending, buckling, and folds, 1724.17 Seismic waves, 179

4.18 Molecules in motion: kinetic theory, heat conduction, and diffusion, 1914.19 Heat transport by radiation, 195

4.20 Heat transport by convection, 197Further reading, 202

Chapter 5 Inner Earth processes and systems, 203

5.1 Melting, magmas, and volcanoes, 2035.2 Plate tectonics, 223

Further reading, 236

Chapter 6 Outer Earth processes and systems, 237

6.1 Atmosphere, 2376.2 Atmosphere–ocean interface, 2486.3 Atmosphere–land interface, 2546.4 Deep ocean, 256

6.5 Shallow ocean, 2636.6 Ocean–land interface: coasts, 2706.7 Land surface, 278

As we began to write this book in the wet year of 2001, Marta’s apartment overlookingthe Galician coast of northwest Spain was beset by winter storms as frontal depressionsran in from the Central Atlantic Ocean over the lush, vegetation-covered granitic out-crops surrounding the Rias Baixas It was here in Baiona Bay on March 1, 1492 thatsuch winds blew “La Pinta” in with the first news of Cristabel Colon’s “discovery” ofthe Americas Now, as then, the incoming moist, warm winds of mid-latitude weathersystems are forced upward to over 1,000 m altitude within 10 km of the coastline caus-ing well over a meter of rain to fall per year (2 m in 2001) Analyses of stream watersfrom far inland reveal telltale chlorine ions transported in as aerosols from sea spray.Warm temperatures and plentiful rains enable growth of the abundant vegetation that

characterizes this España Verde High rates of chemical reaction between soil, water,

and granite bedrock cause weathering to penetrate deep below surface, now revealed

as never before in deep unstable cuttings along the new Autopista to Portugal The

plentiful runoff ensures high rates of stream discharge and transport of water, dissolvedions, and sediment back down to the sea Storms are accompanied at the sea surface bytrains of waves generated far out into the Atlantic whose periodic forms are dissipated

as kinetic energy of breaking water upon coastal outcrops The winter winds gustingover the foreshore mould beach sand into dunes, where untouched by urbanization.Even so, winter storms at high spring tides wash over everything and beat the car parks,

tennis courts, paseos, and lidos back into some state of submissiveness prior to the

concello workmen tidying them all up again in time for summer visitors Now and again

a coastal defense wall falls under the strain and is undercut to helplessness on thebeach below Neither are the rocky outcrops themselves stable, despite their age(300–400 My) and general solidity, for we are not far distant from plate boundariesand faults; the plaster in one of our walls has cracks from a small earthquake whose epi-center was 30 km away at Lugo in 1997 And previous Galician generations wouldhave felt the 1700s Lisbon earthquake much more strongly!

Environment is medio ambiente in the Spanish language, somehow a more apposite and elegant term than the English You, our reader, will have your own medio ambi-

ente around your daily life and in your own interactions with landscape, atmosphere,

and hydrosphere Some environments will be dramatic and potentially dangerous,perhaps under the threat of active volcanic eruption, close to an active plate boundary

or close to a floodplain with rising river levels In order to understand the outer Earthand to manipulate or modify natural environments in a sensitive and safe way it isnecessary to have a basic physical understanding of how Earth physical processes workand how the various parts of the Earth system interact physically – hence our book

It is written with the aim of explaining the basic physical processes affecting the outerEarth, its hydrosphere and atmosphere It starts from basic physical principles andaims to prepare the reader for exposure to more advanced specialized texts thatseldom explain the basic science involved The book is cumulative and unashamedlylinear in the sense that it gradually builds upon what has gone previously Topics

Preface

in simple physics and mathematics are introduced from the point of view of particularexamples drawn from Earth and environmental science The book is distinctive as anintroductory University/College text for several reasons It

1 begins from basic physical principles and assumes little prior advanced physical or ematical background, though the reader/student will be expected to have proceededfurther as the book goes on;

math-2 deals with all aspects of the outer part of Earth, bringing together the physical

prin-ciples that govern behavior of solids (rock, ice), liquids (water, magma), and gases(atmosphere);

3 gives certain derivations from first principles for important physical principles;

4 gives specially drawn and collated figures containing most physical explanation bygraphs, formulae, and physical law

In our general introduction, “Planet Earth and Earth Systems,” we try to set outthe delights and challenges faced by environmental and Earth scientists as they grap-ple with a diverse and complex planet We point forward in this chapter and try toengage the nonspecialist in the wonders of the natural physical world In Chapter 2

we introduce the fundamental principles of “States and Motion,” giving examplesfrom the environmental and Earth sciences wherever possible Chapter 3, “Forces andDynamics,” gets more serious on dynamics and we make frequent reference to mate-rial in the maths Appendix and in the Cookies sections at the end of the book In boththis chapter and the succeeding Chapter 4, “Flow, Deformation, and Transport,” wediscuss the general principles of fluid flow, solid deformation, and thermal energytransfers before discussing specific processes of melting, magma production, volcanicactivity, and plate tectonics in Chapter 5, “Earth Interior Processes and Systems.” Thephysical processes at work in the atmosphere, ocean, and land form the basis for thefinal Chapter 6, “Earth Exterior Processes and Systems.” In both these last chapters

we lay emphasis on the processes that act across the different layers and states thatmake up the outer Earth, a theme we emphasized early on

We are rather humble about what we offer It is not a “Bible” and certainly not theanswer to understanding the universe! We offer a unified view of the very basics of thesubject perhaps We offer signposts and guidelines for further reading and databasesearches We give a maths refresher We put more involved or challenging derivations

in our Cookie boxes at the end of the book We try to combine some physicalprocesses with interesting data about the Earth We use rates of change a lot but thebook doesn’t “do” calculus, so it is mostly a pre-calculus excursion into the physicalworld We stop at the 660 km mantle discontinuity below and at the 12 km tropo-sphere boundary above Why? Because we can’t do everything! Finally, we don’t dochemistry Not because we don’t like it or think its not important, but because, again,

you can’t do everything Cybertectonic Earth surely does combine physics and

chem-istry, but that is another project

Finally, we have spent so much time drawing and redrawing our figures, selectingimages, and carefully considering the content of their headings; they are meant to beread with just as much attention and enthusiasm as the regular text We often put keyitems and explanations into them It is so much easier to follow complicated topicswith them, rather than lots of boring words Well, we hope you enjoy reading andlooking at the diagrams and considering the simple equations as much as we did writ-ing, drawing, and assembling them it’s time to walk the dog adios!

Mike and MartaBrooke and Nigran

Sources, credits, and inspiration for illustrations

Many illustrations in this text are the creation of the authors or of their colleaguesand friends Many have also been assembled, simplified, annotated, and redrawn bythe authors (using Adobe IllustratorTM), often from disparate original sources,including papers from the scientific literature, previously published texts, and websites of noncopyright and governmental organizations The remainder are oftendirectly reproduced, chiefly NASA, SPL, USGS, NOAA, USDA, AGU We

acknowledge the following sources or inspiration for our figures:

Main Text

Fig 1.1 NASA/JPL images; 1.2 Nature 350, 55; 1.6 USDA at Kansas State

University; 1.7, 1.9 USGS; 1.10 K West/Montserrat Volcanic Observatory; 1.11

NOAA/M Perfit; 1.15, 1.16 www.waterhistory.org; 1.17 EOS 83, 382; 1.19

I Stewart Does God Play Dice? (Penguin, 1989); 1.20 A Berger; 2.1, 2.2, 2.3

B Flowers & F Mendoza Properties of Matter (Wiley, 1970); 2.4 NASA image; 2.5

E Linacre & B Geerts Climates and Weather Explained (Routledge, 1997); 2.6

Ocean Circulation (Open University, 2001); 2.7 D Turcotte & G Schubert Geodynamics (Cambridge, 2002); 2.9 A.Vardy Fluid Principles (McGraw-Hill, 1990);

2.11 Pond and Pickard Introductory Dynamical Oceanography (Pergamon, 1983); 2.15 M Pritchard & M Simons Nature 418, 167; 2.16 R McCluskey Journal of

Geophysical Research 105, 2000, 5695; 2.19 M Van Dyke An Album of Fluid Motion

(Parabolic Press, 1982); 3.13-3.18 R Fishbane et al Physics for Scientists and

Engineers (Prentice-Hall, 1993); 3.19 USAF/Bulletin of Volcanology, 30, 337;

3.21 British Meteorological Ofice; 3.28 iceberg 3.31 USDA image; 3.35, 3.36

Ocean Circulation (Open University, 2001); 3.38, 3.39 Pond and Pickard, Introductory Dynamical Oceanography (Pergamon, 1983); 3.43 R Roscoe British

Journal of Applied Physics, 3, 267 and M Leeder Sedimentology and Sedimentary Basins (Blackwell, 1999); 3.48 R Falco Physics of Fluids, 20, 124; 3.50-3.52;

J.R.D Francis A Textbook of Fluid Mechanics (Arnold, 1969); 3.53, 3.54, 3.56A

M Van Dyke An Album of Fluid Motion (Parabolic Press, 1982); 3.58 G Davis &

S Reynolds Structural Geology (Wiley, 1996); 3 74 R Twiss & E Moores Structural

Geology (Freeman, 1992), 3.79 P Molnar & P Tapponier (Science, 189, 419), 394

N Price & J Cosgrove Analysis of Geological Structures (Cambridge, 1990), 3.101,

D Griggs et al., Geological Society of America, Memoir 79, 3.102 A F Donath

American Scientist, 58, 54, 4.6, 4.7, 4.9 O Reynolds Proceedings of the Royal Society

1883; 4.8 M Van Dyke An Album of Fluid Motion (Parabolic Press, 1982); 4.11A

ibid; 4.12 R.A.Bagnold Physics of Wind-blown Sand and Desert Dunes (Chapman

Hall, 1954); 4.13 A Grass, Journal of Fluid Mechanics, 50, 233; 4.16 D Tritton

Physical Fluid Dynamics (Oxford 1988); 4.17 M Coward Journal of the Geological

Acknowledgments

Society London 137, 605; 4.18B-D S Kline, Journal of Fluid Mechanics, 30, 741;

4.18E M Head Journal of Fluid Mechanics, 107, 297; 4.19 J Best Turbulence;

Perspectives on Flow and Sediment Transport (Wiley, 1993); 4.20-4.22 A Grass,

Journal of Fluid Mechanics, 50, 233; 4.23 D Tritton Physical Fluid Dynamics

(Oxford 1988); 4.24 A Grass, Journal of Fluid Mechanics, 50, 233; 4.28 image

cour-tesy of A Cherkaoui; 4.33 M Samimy et al A Gallery of Fluid Motion (Cambridge, 2003); 4.31 M Van Dyke An Album of Fluid Motion (Parabolic Press, 1982),

R Gibbs Journal of Sedimentary Petrology, 41, 7; 4.35 W Chepil Proceedings Soil

Science Society of America 25, 343; USDA/Kansa State University; M Miller Sedimentology, 24, 507; 4.44 M Van Dyke An Album of Fluid Motion (Parabolic Press,

1982); 4.45 J.S Russell British Association for the Advancement of Science, 1845,

311; 4.48 M Van Dyke An Album of Fluid Motion (Parabolic Press, 1982), D Tritton

Physical Fluid Dynamics (Oxford 1988); 4.49-4.52 R Tricker, Bores, Breakers, Waves and Wakes (Mills and Boon, 1964); 4.53 D Tritton Physical Fluid Dynamics (Oxford

1988); 4.56 K Tietze; 4.60 H Makse; 4.62 A.C Twomey/SPL; 4.65, 4.66 T Gray

et al Sedimentology, 52, 467; 4.67 Edwards Sedimentology, 41, 437; 4.69A USGS; 4.69B Nichols Sedimentology, 41, 233 4.73 R Gimenez; 4.80 J Suppe Principles of

Structural Geology (Prentice- Hall, 1985);4.84-4.87 R Twiss & E Moores Structural Geology (Freeman, 1992); 4.91 R Twiss & E Moores Structural Geology

(Freeman, 1992); 4.106 W Hafner, Bulletin Geological Society of America, 62, 373;

4.109B, 4.110B, 4.112B NASA;4.120, 121 J Ramsay Folding and Fracturing of

Rocks (McGraw-Hill, 1967); 4.124-4.126 R.Twiss & E Moores Structural Geology

(Freeman, 1992); 4.127 USGS; 4.131, 4.133 - 4.137 B Bolt Inside the Earth, (Freeman, 1982); 4.138, 4.140 USGS; 4.141 B Bolt Inside the Earth, (Freeman, 1982) 4.142C USGS; 4.143-4.144 R Fishbane et al Physics for Scientists and

Engineers (Prentice-Hall, 1993); 4.150 J.G Lockwood, Causes of Climate (Arnold,

1979); 4.151-4.152 D Tritton Physical Fluid Dynamics (Oxford 1988); 4.153-4.159

M Van Dyke An Album of Fluid Motion (Parabolic Press, 1982); 5.2 EOS

Transactions AGU;5.3 J.G Moore/USGS; 5.4 www.stromboli.net; 5.5 Hatch et al

Petrology of the Igneous Rocks (George Allen and Unwin, 1961); 5.10 D Latin in Tectonic Evoution of the North Sea Rifts (Oxford, 1990); 5.12, 5.13, 5.14 I Kushiro,

in Physics of Magmatic Processes, (Princeton, 1980); 5.15 USGS; 5.16, 5.17 H.S Yoder, Generation of Basaltic Magma (National Academy of Sciences, 1976); 5.19 J Elder, The Bowels of the Earth (Oxford, 1976); 5.20 USGS; 5.21A New

Mexico School Mines; 51.21B C Tegner & http:77www.geo.au.dk/English/

research/minpetr/mcp/pge/; 5.23 I Kushiro, in Physics of Magmatic Processes, (Princeton, 1980); 5.24 H Shaw, in Physics of Magmatic Processes, (Princeton, 1980); 5.25A J Elder, The Bowels of the Earth (Oxford, 1976); 5.27 USGS; 5.29, 5.30, 5.31, 5.31 R Cas & J Wright Volcanic Successions (Allen & Unwin, 1988); 5.32 USGS;

5.33 A Matthews & J Barclay Geophysical Research Letters, 31 (5), LO 5614; 5.34

USGS/JPL/NASA; 5.35 A Cox & R.B Hart Plate Tectonics; How it Works

(Blackwell, 1986); 5.36 N.Pavoni EOS 86/10; 5.37, 5.38; 5.39 C Fowler The Solid

Earth (Cambridge, 1990); 5.40, 5.41 D Turcotte & G Schubert Geodynamics

(Cambridge, 2002); 5.42 D Forsyth and S Uyeda Geophysical Journal of the

RoyalAstronomical Society 43, 163; A Cox & R.B Hart Plate Tectonics; How it Works

(Blackwell, 1986); 5.43 M Leeder Journal of the Geological Society, London 162,

549; 5.44A R.Twiss & E Moores Structural Geology (Freeman, 1992); 5.45

J Dewey & R Shackleton Transactions of the Royal Society 327, 729; 5.46 P.Silver &

R Carlson Annual Reviews Earth and Planetary Sciences, 16, 477; 6.1 J.G Lockwood

Causes of Climate (Arnold, 1979); 6.2, 6.3 J.T Kiehl, Physics Today, Nov issue, 36,

1994; 6.4 Inspired by A Matthews; 6.5, 6.6 E Linacre & B Geerts Climates and

Acknowledgments xi

Weather Explained (Routledge, 1997); 6.7 F.H Ludlam Clouds and Storms (Penn

State University, 1980); 6.9 J.G Lockwood Causes of Climate (Arnold, 1979); 6.10

P Brimblecombe and T Davies, in Encyclopaedia of Earth Sciences (Cambridge, 1982); 6.12 J Imbrie and K.P Imbrie Ice Ages: Solving the Mystery (MacMillan,

1979); 6.13 Carl Friehe; 6.15 M.D Powell et al Nature, 422, 279, 2003; 6.16

Ocean Circulation (Open University, 2001); 6.17 SEAWIFS Project, Nasa/Goddard

SFC; 6.18 H.E Willoughby Nature, 401, 649; 6.19 I Wilson, Geographical Journal,

137, 180; 6.20A SEAWIFS Project, Nasa/Goddard SFC; 6.20C N.J Middleton et al.

in Aeolian Geomorphology (Allen and Unwin, 1986); 6.21, 6.22, 6.23 Ocean

Circulation (Open University, 2001); 6.24 TOPEX-Poseidon satellite image; 6.25

Ocean Circulation (Open University, 2001); 6.26 NOAA; 6.27 L Fu et al EOS 84,

241; 6.28 Pond and Pickard, Introductory Dynamical Oceanography (Pergamon,

1983); 6.29, 6.30 Schmitz & McCartney, Reviews Geophysics, 31, 29; 6.31 Mulder

et al EOS, 22 Oct 2002; 6.32 P.E Biscaye & S.L Eittreim, Marine Geology, 23, 155;

6.33 D Swift Shelf Sediment Transport (Dowden, Hutchinson & Ross, 1972); 634,

6.35 C Nittrouer & L.D Wright, Reviews Geophysics, 32, 85; 6.36 R Haworth, in

Offshore Tidal Sands (Chapman Hall, 1982); 6.37 Waves, Tides & Shallow-Water Processes (Open University, 1999); 6.38, 6.39 N Wells, The Atmosphere and Ocean

(Taylor and Francis, 1986); 6.40 Waves, Tides & Shallow-Water Processes (Open University, 1999); 6.41 Offshore Tidal Sands (Chapman Hall, 1982); 6.42 W Duke

Journal of Sedimentary Petrology, 60, 870; 6.44 C Galvin Journal of Geophysical

Research, 73, 3651; 6.45 Waves, Tides & Shallow-Water Processes (Open University, 1999); 6.47 M Longuet-Higgins & R Stewart Deep-Sea Research 11, 529; 6.47, 6.48 Bowen et al Journal of Geophysical Research, 73, 256; 6.49 Pritchard and Carter,

in The Estuarine Environment (American Geological Institute, 1971); 6.50

R Kostaschuk et al., Sedimentology, 39, 205; 6.51 I Grabemann & G Krause,

Journal of Geophysical Research, 94C, 14373; 6.52, 6.53 A Mehta Journal of Geophysical Research, 94, 14303; 6.54 Landsat Image; 6.57 M Leeder et al Basin

Research 10, 7; 6.61 Chikita et al Sedimentology, 43, 865; 6.62 Wetzel, Limnology

(Saunders, 1983); 6.65 J Bridge; 6.67 J Best; 6.68B N.D Smith; 6.69 I Wilson,

Geographical Journal, 137, 180; 6.73 J Dixon; 6.75, 6.76 I Wilson, Geographical Journal, 137, 180; 6.77, 6.78 NASA; 6.79 Alley et al Nature, 322, 57; 6.81 Harbor

et al Geology, 25, 739; 6.82 EOS, exact source unknown; 6.83 NASA/Scott Polar

Research; 6.84 http://glaciers.pdx.edu/gdb/maps/home.php

Cookie figures

2 Pond and Pickard, Introductory Dynamical Oceanography (Pergamon, 1983); 3,4 J.R.D Francis A Textbook of Fluid Mechanics (Arnold, 1969); 5, 7 M.W Denny, Air

and Water (Princeton, 1993); 8 P Rowe, Proceedings Royal Society London 269, 500;

9 R Bagnold, Proceedings Royal Society 225, 49.

We also thank referees Jenni Barclay, Adrian Mathews, Chris Paola, and DaveWaltham for their different perspectives on a wide-ranging subject, for help in making

us focus our approach in this difficult endeavor and for rescuing us from some errors.Also thanks to Ian Francis, Delia Sandford, and Rosie Hayden of the Blackwell team,for their faith in the project and for their great help in its evolution from plan toexecution

1.1.1 Lateral thinking from general principles

Physical processes on Earth and other planets must obey

the same basic physical laws, depending in detail on the

nature of the particular planetary environment, for example

physical composition and gravity While this book is obviously

concerned with Earth processes, it would be

narrow-minded of us not to pause for a moment right at the start

and make some comparisons between Earth and our three

nearest neighbor rocky planets This turns out to be the

beginning of a stimulating intellectual and practical

exer-cise Why so? An anecdote will help explain our point

In the early 1970s, the desert explorer, soldier, andhydraulics engineer R A Bagnold, who helped create the

scientific discipline of loose-boundary hydraulics, was

con-tacted by NASA to undertake consultancy regarding

ongoing orbital and future lander missions to Mars The

background to this strange request from the world’s most

prestigious space outfit to a retired brigadier of engineers

was that NASA scientists had been appalled and intrigued

by the enormous planetary dust storm that covered the

planet for the first 2 months of the Mariner 9 mission

Although the storms died down in late January 1972,

revealing a fabulous dune-covered landscape, like the

Sahara in places, NASA wondered if the planetary winds

were so severe that ground conditions would be inimical

to survival of the planned lander mission This was an

espe-cial worry in the face of the failure of contemporary

Russian Mars 3 orbiter and lander missions: the latter had

arrived in the middle of sandstorms and never transmitted

more than a few seconds of data back to Earth

Bagnold’s work was the key here Working from firstphysical principles and making use of breakthroughs in

fluid dynamics achieved in the 1920s and 1930s, he had

discovered, by judicious use of experiment, field observation, and theory, the immutable physical laws thatgoverned the transport of sand and silt particles in theEarth’s atmosphere, especially in the concentrated layersclose to the ground surface during sandstorms NASAasked Bagnold advice on how to modify his earthboundphysical laws for application to the Red Planet Bagnoldand his collaborator C Sagan had to take due account ofthe Martian atmosphere, surface, and rock properties,such as were then known: they had to find accurate valuesfor gravitational acceleration, air density, rock density, andsurface wind velocity Then they had to calculate the likelyextent and severity of sand blasting, dust transport, andpossible effects on the landers The results are of contin-ued interest in view of plans to land humans on Mars earlythis millennium

How to characterize a planet (Fig 1.1)? There are intrinsic

properties of solid size (diameter d) and mass (m) from

which we can compute mean planetary density (p) and

gravitational acceleration (g) Then the nature of any

atmospheric envelope, its surface pressure (ps), and

tem-perature (ts) Also its mass, composition, and thickness.Astronomical information includes distance from the Sun,

rate of planetary spin (length of day Ld), rate of revolution

about the Sun (length of year Ly), and inclination of the

equator with respect to orbit (Ie) The regularity andeccentricity of the orbit are of additional interest We wish

to know the mean chemical compositions of the solid and gaseous components and whether the planet has inter-nal layering that might separate distinctive functioning

1 Planet Earth and Earth

systems

1.1 Comparative planetology

2 Chapter 1

From Sun to ( ⭈10 6 km)

O2 0.13 High orbital ellipticity.

Long rifts, extinct volcanic forms

Southern half cratered Molten mantle, no active plate tectonics

No surface water today but runoff earlier in history

Oxidative aqueous rock weathering Perennial polar water-ice caps Wind blown dust

500–600 km outer silicate

“crust.” Partially molten

Fe core: weak magnetic field

Atmospheric gases %:

Radar mapped by Magellan.

Low orbital eccentricity.

“Runaway” greenhouse atmosphere.

Spectacular extinct volcanoes and rift valleys

Some active hot spots.

Convecting molten mantle No magnetic field

71% water covered, but oceans less known than Venus Surface life

Oxygen-rich atmosphere Soil